Top Retaining Walls Lower Hutt builds timber crib retaining walls in Lower Hutt for banks where a gravity wall makes more sense than a post wall. A crib holds ground with its own weight rather than deep footings, which suits hill sites where getting a 1.5m post hole in is awkward or where the ground below changes character over a short distance.
Crib walls use H5 headers and stretchers laid in alternating tiers, a bit like a log cabin with open cells. The first stretcher course sits on a concrete foundation or a well compacted base to lock in the batter, then the wall builds up with granular drainage material packed into each layer as it rises.
The whole structure leans back into the bank at roughly one in four. That backward lean, plus the weight of the fill, is what works against the soil pushing on it.
| Units | H5 treated timber headers and stretchers |
|---|---|
| Batter | About one in four backward lean |
| Base | Concrete foundation or compacted granular base |
| Backfill | Granular drainage material, placed in layers |
| Front cells | Can be soil filled and planted |
| Best for | Wide banks and sites where deep post holes are hard |
A crib wall is only as good as what goes inside it. The cells take granular drainage material, not the spoil that came out of the bank. Clean metal gives the wall its mass, drains freely and stops pressure ever building behind the face.
We have taken apart crib walls in the Hutt that were backfilled with weathered greywacke clay off the site. They hold water, they slump, and the timber rots from the inside where nobody can see it happening.
Around Stokes Valley, Kelson and Belmont there are plenty of banks too wide for a post wall to be economic and too steep to leave alone. A crib spreads its load over a broad base instead of relying on individual footings, which is useful where the ground changes every few metres.
Fill the front cells with topsoil and plant them, and within a couple of seasons the wall reads as a green bank rather than a structure.
Every wall we build gets drainage. At least 300mm of clean free draining metal, a perforated coil at the base running to a real outlet, and geotextile over the top so silt cannot block it. It is not an optional line on our quotes.
Not usually per metre, because there is more material and more backfill in it. It wins where deep post holes are impractical, or where you want a face you can plant.
Yes, with engineering and consent. Terraced crib walls with real horizontal separation are a common way to handle a tall bank without one big engineered structure.
The granular fill does most of the work, but we still run a coil at the base so water leaves the foundation rather than ponding there.
Our old wall was rotten right through and leaning into the neighbour's place. They pulled the lot out, put proper drainage behind the new one and had it finished in three days. Swept the site clean every afternoon before they left too. Tidiest crew we have ever had here by a long way.
They sorted the consent, which was the bit I was dreading. Dealt with the council so I never had to, and kept me in the loop the whole way through. The driveway sits right above it and has not shifted a millimetre.
Steep section, shocking access, and they still made it look easy. They suggested two smaller walls instead of one big one, which saved us thousands in engineering fees. The terrace in between is now my favourite part of the whole garden.
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